PROJECT SUMMARY/ABSTRACT Platelet BioGenesis has developed a millifluidic bioreactor that reproduces key features of the adult bone marrow microenvironment to enable clinical-scale production of donor-independent platelets (PLT+) from human induced pluripotent stem cells (hiPSCs). Based on guidance from the U.S. Food & Drug Administration (FDA), the goal of this proposal is to perform safety and efficacy studies following good laboratory practice (GLP) principles to support a regulatory package that will permit clinical testing of our product. Platelets are essential blood components responsible for clot formation and blood vessel repair. Low platelet count is a dangerous consequence of cancer treatment, transplant, and surgery, and platelets are a critical first-line therapy to prevent uncontrolled bleeding. Transfusion units are derived exclusively from human volunteer donors and must be stored at ?22C to avoid irreversible activation/aggregation. Risk of bacterial growth limits shelf life to 5 days, 3 of which are consumed by screening and transport. Because of these limitations, blood centers often only have a 1.5-day inventory that is quickly depleted by emergencies [1,2]. We have developed a 2-step ex vivo production platform in which hiPSCs (replenishable progenitors that can be frozen for years) undergo differentiation into pre- megakaryocytes (preMK+) that are banked and used for on-demand PLT+ generation in our bioreactor. In our Phase II project, we successfully generated and characterized functional preMKs+ and PLTs+ from a qualified hiPSC line [3,4] using an established serum/feeder-free, scalable current good manufacturing practice (cGMP)-compliant process [5]. After confirming PLT+ quality and function, we verified hemostatic and thrombogenic potentials in vivo. Building on these results, this Phase IIB SBIR proposal outlines three specific aims to perform GLP studies to 1) establish PLT+ release criteria and storage profile, 2) assess teratoma risk in vivo, and 3) measure circulation and clearance time in vivo. For all aims, human donor platelets will serve as a physiological benchmark for comparison. Completion of these aims will facilitate submission of an Investigational New Drug (IND) application. Aim 1. Establish PLT+ release quality and storage profile. We will evaluate PLT+ biomarkers, function, metabolic activity, and sterility under FDA-approved storage conditions. Aim 2. Assess teratoma risk in mice. Following GLP guidelines, we will determine whether any risk of tumorigenic growth is associated with PLT+ product in immunocompromised (NSG) mice. Aim 3. Assess PLT+ circulation and clearance times in mice. We will assess the circulation and clearance of PLT+ in immunocompromised (NSG) mice.